Abstract
High-performance terahertz (THz) imaging devices have drawn wide attention due to their significant application in a variety of application fields. Recently, the upconversion device based on the integrated homo-junction interfacial workfunction internal photoemission detector and light-emitting diode (HIWIP-LED) has emerged as a promising candidate for broadband THz upconversion pixelless imaging device. In this paper, systematical investigations on the cryogenic-temperature performances of the LED part in HIWIP-LED devices, including electroluminescence (EL) spectra and the EL efficiency, have been carried out by elaborating the radiative recombination mechanism in the quantum well, internal quantum efficiency, and the light extraction efficiency (LEE) both experimentally and theoretically. On this basis, we have further studied the operation mode of the HIWIP-LED and concluded that the LEE could directly determine the upconversion efficiency. A numerical simulation has been performed to optimize the LEE. Numerical results show that the device with a micro-lens geometry structure could significantly improve the LEE of the LED thereby increasing the upconversion efficiency. An optimal upconversion efficiency value of 0.12 W/W and a minimum noise equivalent power (NEP) of 14 pW/Hz1/2 are achieved using the micro-lens structure together with anti-reflection coating. This work gives a precise description of cryogenic LED performance in the HIWIP-LED device and provides an optimization method for the broadband HIWIP-LED THz upconversion pixelless imaging device.
Highlights
Up-converting long-wavelength infrared (IR) light to shorter-wavelength radiation has attracted more attention and has been intensively explored in the last two decades thanks to its tremendous potential in low-cost and large-format IR/terahertz (THz) imaging, high-efficiency solar cells, and sensitive biological imaging [1,2,3,4]
The IR signal at the range of 8–12 μm was first detected by the quantum well IR photodetector (QWIP), and the produced photocurrent was injected into the active region of the light-emitting diodeOptimization of THz Upconversion Imaging (LED) resulting the extra near infrared (NIR) emission under bias voltage [5, 6]
How to improve the upconversion efficiency is an urgent problem for homojunction interfacial workfunction internal photoemission (HIWIP)-LED pixelless imaging devices
Summary
Up-converting long-wavelength infrared (IR) light to shorter-wavelength radiation has attracted more attention and has been intensively explored in the last two decades thanks to its tremendous potential in low-cost and large-format IR/terahertz (THz) imaging, high-efficiency solar cells, and sensitive biological imaging [1,2,3,4]. How to improve the upconversion efficiency is an urgent problem for HIWIP-LED pixelless imaging devices.
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